1. Field of the Invention
The present invention relates to a data structure for searching for or managing desired content data. In particular, the present invention relates to a data structure and a data search technique capable of reliably preventing tampering of records of information such as attribute information of content data.
2. Related Art
In a distributed content storage system of this kind, each node apparatus can acquire desired content data from another node apparatus or a content management server by using content catalog information containing attribute information of content data. The attribute information includes information such as content names, publish dates, expiration dates, and keywords for searching content data. The content catalog information is generated by a content management server, for example, and distributed by the content management server to node apparatuses. When new content data is added to the distributed content storage system or content data has expired, the content management server updates the content catalog information and distributes the updated catalog information to the node apparatuses.
The data amount of content catalog information increases as the number of items of content data available in the distributed content storages system increases. This has posed a problem that content catalog information overflows a single node apparatus. To solve the problem, a configuration has been proposed in which content catalog information is split into multiple pieces and the pieces of content catalog information are distributed over and stored in multiple node apparatuses.
When each node apparatus stores the split content catalog information, a digital signature needs to be added to the attribute information of each item of content data in order to prevent tampering of the content catalog information.
Adding, updating, or deleting attribute information of content data in content catalog information involves searching for the content catalog information. Specifically, the location where the content catalog information is to be inserted, updated or deleted needs to be searched for. Conventional systems are inefficient because an entire list of items of content catalog information to which digital signatures have been applied needs to be searched through for desired content data.